RFR: JDK-8145391: Updated jprt.properties, devtools, jib and readme with SS12u4

[Erik Joelsson]

The default compiler for Solaris was changed in build 96. The jprt 
configuration, jib, devtools and readme needs to be updated to reflect 
this. In the readme, there are some other left overs from other compiler 
changes that also need to be tweaked.

Bug: https://bugs.openjdk.java.net/browse/JDK-8145391
Webrev: http://cr.openjdk.java.net/~erikj/8145391/webrev.01/
/Erik